Electric blasting initiator



My 24, 1938. c, A, W DBURY 2,118,533

ELECTRIC BLASTING INITIATOR Filed Nov. 19, 1936 CiifforaAl l oodbz/lr INVENTOR.

ATTORNEY.

' Patented May 24, 1938 PA'H'EN OFFIC- ELECTRIC BLASTING mrmrroa Cliflord A. Woodbury, Media, Pa., assignor to E. I. du Pont de N emours & Company, Wilmington, Del., a corporation of Delaware Application November 19, 1936, Serial No. 111,583

9 Claims.

The present invention relates to electric blasting initiators, and more particularly to an improved ignition composition for such initiators.

Electric blasting initiators are of two general types, depending on the character of the main explosive charge to be initiated. Detonation of high explosives of the dynamite type is accomplished by means of an electric blasting cap,

whereas the initiation of defiagrating explosives 10 such as black powder is achieved by a flameproducing means such as an electric squib.

Although these two types of electric blasting initiators are clearly distinguished in purpose and effect, they both employ a composition which is readily ignited by an electrical heated wire. In the case of blasting caps, this ignitable composition serves to initiate a sensitive detonating base charge, whereas in the squib type of initiator it ignites either the main explosive charge directly, or an auxiliary defiagrating base charge in the squib.

Ignitable compositions employed either in detonators or in squibs should possess low and uniform firing current properties which are easily duplicated in the manufacturing operation. For electric squibs, the ignition composition should possess, in addition to the low firing current requirements, the ability to develop on combustion a hot flame of considerable duration. This latter property is of especial importance when the squib is employed with moist pelleted black powder, which condition frequently obtains in wet coal mines. While many ignition compositions possess one or the other of these necessary properties, it is a fact well recognized in the art that few are available which have both of these characteristics to the desired degree.

The object of the present invention is a new and improved ignitable composition which is sat- 40 isfactory with respect to low firing current requirements and which produces a hot flame of considerable duration. A further object is an electric initiator containing an improved base charge. A still further object is an electric squib of such a design that it will cause ignition of defiagrating explosives under the most adverse conditions. I the invention is hereinafter described.

- I have found that the foregoing objects are accomplished by employing a composition comprising ground smokeless powder and black powder. Such a composition requires only a low firing current for ignition, and on firing, it produces a hot flame of long duration.

While the proportion of the ingredients-may Other objects will be apparent as vary within wide limits, I prefer to use a composition comprising from 30 to 50% black powder and from 70 to 50% ground smokeless powder. The composition may be grained, if desired, with a suitable solution. A blend of approximately 40% black powder and 60% ground smokeless powder may be used to illustrate the properties of my improved composition. Such a composition has a readily standardized firing current of about 0.330 ampere, a high rate of deflagration, and a hot flame of long duration. While the composition described in the foregoing may be employed in electric blasting initiators, generally, for example in detonators as an ignition composition, where slow action is desired, I prefer to use it in electric blasting squibs. Furthermore, to avoid misfires in series firing, I prefer to employ my improved composition with initiators provided with a bridge wire of slow-fusing characteristics, such as that disclosed and claimed in'copending application, Serial No. 111,581, filed November 19, 1936. It may be employed, how-* ever, with the usual type of bridge wire, if desired.

The superior properties of my improved composition make it especially effective when used in the closed shell type of squib, the shell being of copper, aluminum or other metal. Under such conditions of use, the ignition of the charge causes the development of pressure withm the shell. When the latter bursts under this pressure, the deflagrating explosive immediately surrounding the squib is pulverized or disintegrated somewhat by the force of the release, and the ignition of the main explosive charge is thereby facilitated. This eflect is especially advantageous where moist pellets of black powder are to be initiated.

In order to describe my invention more clearly,

' I shall refer to the attached schematic diagrams of two embodiments of my invention. It is understood, however, that this is'done solely by way of illustration and is not to be construed as a limitation upon the scope of my invention.

Figure 1 is a vertical elevation of one form of closed shell electric squib in accordance with my invention, while Figure 2 is a similar elevation of another form of. closed shell electric squib. Similar characters are used in the drawing and the accompanying description to indicate corresponding parts of the respective views.

Figure 1 illustrates one form of electric squib in accordance with my invention. I represents a metal shell of any suitable material, such asaluminum, for example. At the bottom of this shell is a combined base and ignition charge 2 comprising approximately 40% black powder and 60% ground smokeless powder, the composition having been grained by a suitable solution. A slow-fusing bridge wire 4, such as that disclosed and claimed in copending application Serial No. 111,581 filed November 19, 1936, connecting the leg wires 5, which are held in position by a bridge plug 6, is surrounded by the ignition composition 3 so that the heating of the bridge wire will fire the composition 3. The detonator is closed by waterproofing compositions I and a sulfur seal 8.

Figure 2 illustrates another form of electric squib according to my invention. I represents a shell of aluminum or other suitable material. I prefer to employ a light walled aluminum shell whichmay be weakened at the base in any suitable manner, if so desired. At the bottom of the shell is placed a base charge 2 of black powder suitably pressed into the shell. This is covered by a loose ignition charge 3 comprising approximately 40% black powder and 60% ground smokeless powder grained with gum arabic. The leg wires 5 held in position by the bridge plug 6 are joined by the slow-fusing bridge wire 4 of the type described in the copending application above referred to, which is surrounded by the ignition composition 3. The squib is closed by means of a waterproofing composition 1 and a sulfur seal 8.

It is to be understood that these embodiments are cited by way of illustration only and are not to be construed as limitations on my invention. In the foregoing detailed description, it is apparent that many variations can be made without departing from the spirit and scope of the invention. Thus,for example, my improved composition may also be employed in detonators, delay detonators, delay squibs, and generally in all types of initiators if desired. Furthermore, the composition may be used as a pressed charge, a loose chargefor as a cemented charge with any type of conventional electrical firing means, including matchheads, concave plugs, bridge plugs and the like. Many other variations will be apparent to those skilled in the art. I intend, therefore, to be'limited only in accordance with the following patent claims:

I claim:

1. A blasting initiator containing a composition wherein the explosive ingredients consist of a substantially homogeneous blend of black powder and ground smokeless powder.

2. An electric blasting initiator containing a charge of a composition wherein the explosive ingredients consist of a substantially homogeneous blend of. 30 to black powder and 70 to 50% ground smokeless powder.

3. An electric blasting initiator containing a loose charge of a composition wherein the explosive ingredients consist of a substantially homogeneous blend of approximately 40% black powder and approximately ground smokeless powder.

4. An electric blasting cap containing a charge of an ignition composition wherein the explosive ingredients 1 consist of a substantially homogeneous blend of black powder and ground smokeless powder.

5. An electric squib containing a composition wherein the explosive ingredientsconsist 01a substantially homogeneous blend of black powder and ground smokeless powder.

6. An electric squib containing a loose charge of a composition wherein the explosive ingredients consist of a substantially homogeneous blend of 30 to 50% black powder and to 50% ground smokeless powder.

7. An electric squib comprising a closed metallic shell and a loose charge of an ignition composition within said shell, the explosive ingredients of. said ignition composition consisting of a substantially homogeneous blend of 30 to 50% black powder and 70 to 50% ground smokeless powder.

8. An electric squib comprising a closed metallic shell, a pressed base charge of black powder and a loose charge of an ignition composition wherein the explosive ingredients consist of a substantially homogeneous blend of 30 to 50% black powder and 70 to 50% ground smokeless powder.

9. An electric squib comprising a closed metallic shell, a pressed base charge of black powder and a loose charge of an ignition composition wherein the explosive ingredients consist of a substantially homogeneous blend of approximately 40% black powder and 60% ground smokeless powder.

CLIFFORD A. WOODBURY. 

